Electric motor drive, in particular fan drive

ABSTRACT

An electro-motor drive, in particular for a fan drive of a motor vehicle, includes a commutator motor, a motor shaft of which is rotatably mounted on axially opposite sides in shaft bearings facing away from the bearing shield in order to substantially dampen the sound of at least bearing play-related contact noise and vibration or humming noise.

This nonprovisional application is a continuation of InternationalApplication No. PCT/DE2009/001777, which was filed on Dec. 16, 2009, andwhich claims priority to German Patent Application No. DE 10 2008 062432.2, which was filed in Germany on Dec. 17, 2008, and which are bothherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns an electric motor drive with a commutator motorwhose motor shaft is rotatably supported in shaft bearings on axiallyopposite sides.

2. Description of the Background Art

Known from EP 182 145 A1, which corresponds to U.S. Pat. No. 4,639,193,and from DE 199 09 507 C1, which corresponds to U.S. Pat. No. 6,283,726,are fans of a heating and air conditioning system of a motor vehiclewith an electric-motor-driven fan rotor that is mounted on the motorshaft.

Furthermore, it is known from DE 295 13 633 U1 for the motor shaft to berotatably supported in plain bearings implemented as spherical bearings,both on the brush system side (BS) where the commutator bars of themotor are located and on the opposing other side (AS). The sphericalbearings in this design are pressed against an end plate by means of aclamping collar. On the BS side, a shaft section of the motor shaft, towhich the fan rotor is attached by its central rotor hub, projects outof the end plate near the commutator. Such electric motor drives have anaxial play of the motor shaft, and thus of the motor armature/impellersystem, which frequently results in undesirable noises.

SUMMARY OF THE INVENTION

It is therefore an object of the invention is to improve an electricmotor drive of the type mentioned at the outset with regard to the leastpossible noise generation.

To this end a damping system for sound damping is located on a bearingside, facing away from the end plate, of the shaft bearing on theBS-side and/or the shaft bearing on the AS-side. The damping systemserves to reduce the sound level, especially of impact noises caused bybearing play, but also serves to damp so-called “ooo” sounds (whiningnoises), which are produced by operation-related disturbances at eachrotation of the motor and associated resonance effects.

The invention is based on the idea that the operationally caused noisesof such a fan drive are, on the one hand, impact noises that are causedby an axial excursion of the motor shaft and the impeller system placedthereon. On the other hand, the passage of the brushes over thecommutator shaft additionally causes vibration noises, which are emittedthrough the motor housing. In this process, the noise generation insidethe motor originates from the commutator through the shaft bearing andend plate to the motor housing.

This structure-borne sound, which can also be generated by themulti-spoke fan rotor and is transmitted to the motor housing, arises ina speed range of the electric or commutator motor that is correlatedwith the resonant frequencies of the overall system, in particular atresonant points specific to the housing parts. If the sound transmissionpath from the commutator on the one hand, and from the fan rotor on theother hand, through the shaft bearing to the motor housing can beeliminated or at least reduced, then the structure-borne sound can alsobe reduced accordingly.

On the other hand, impact noises resulting from axial excursion of thesystem parts coupled to one another by the motor shaft, namely thearmature and the commutator of the motor, as well as those caused by thefan rotor of the fan, can be prevented or at least reduced if a suitabledamping device is placed on the bearing side facing away from the endplate of the applicable shaft bearing in order to attenuate thebearing-play-related impact noises.

In addition to damping the impact noises that are prevented or reducedon the BS side by the damping system that is used, in practice, betweenthe commutator and the shaft bearing there and that takes up the axialplay, the vibrations generated by the interaction between the brushesand the commutator bars also are damped reliably by means of the dampingsystem.

In a useful embodiment, the damping system has a sealing disk and athrust washer with antifriction properties that is referred to below asa sliding disk. A spring travel is appropriately defined between thesealing disk and the sliding disk that usefully is in the range oftenths of a millimeter, and preferably is less than or equal to 0.2 mm.Located between the sealing disk and the sliding disk, a wave spring inthe manner of a spring washer or a spring element, is located on themotor shaft. This wave spring contributes significantly, or evenpredominantly, to attenuating the whining or “ooo” sounds.

Suitably, the damping system has a damping element on the disk side ofthe sealing disk facing the shaft bearing. This damping elementpreferably is annular. In the assembled state of the sealing system, thewave spring is suitably disposed in an annular space formed between thedamping element of the sealing disk and the motor shaft, so that thedamping element surrounds the wave spring coaxially.

Moreover, the sealing system preferably also has a shaft seal betweenthe sealing disk and the rotor shaft. To this end, the sealing disk, thedamping element, and the shaft seal are preferably produced as a singlepiece from a two-component plastic in the injection molding process. Thesealing disk in this design is made of a relatively hard material orsubstance, while the shaft seal, which in turn is a single piecetherewith, is made of a relatively soft damping material. Athermoplastic elastomer is particularly suitable as the dampingmaterial.

The shaft seal, which like the damping element is annular or cylindricalin shape, is L-shaped in cross-section. An axial branch of the L,extending along the rotor shaft, of the corresponding cylindrical orjacket-like section of the shaft seal produces a reliable press fit ofthe sealing disk on the motor shaft. Adjoining this axial branch of theL, a radial branch of the L of the corresponding annular section of theshaft seal engages behind the sealing disk on the rear of the diskfacing away from the shaft bearing. This radial branch of the L of theshaft seal and, where applicable, a number of damping points preferablyimplemented as arcs or segments of circles, which likewise are made ofthe comparatively soft damping material, also serve as damping elementsof the damping system in its contact with the commutator.

In a useful development, the sealing disk and the sliding disk areslotted together. For this purpose, detent elements are suitably formedon the sealing disk, preferably three detent elements arranged to beoffset by 120° with respect to one another. The detent elements arecomposed of detent webs that are oriented toward the sliding disk.Formed on the end sides of the detent webs, at a predetermined distancefrom the sealing disk or the damping element that is a single piecetherewith, are detent cams, which engage behind the sliding disk in theslotted-together state. The spring travel between the sealing disk andthe sliding disk that is available to the spring element is defined bythe axial thickness of this sliding disk and by the distance of thedetent cams from the damping element of the sealing disk.

Formed on the circumferential side of the sliding disk—again usefullyoffset by 120° with respect to one another—are outwardly projectingcarrier elements or carrier cams. When the sliding disk is in theslotted state, these carrier elements produce an interlocking connectionwith the sealing disk in the appropriate direction of rotation of themotor or motor shaft as soon as the detent cams have traversed or passedthrough the distance, measuring e.g. 120° of arc, between two detentelements of the sealing disk, upon first startup.

It is useful for the mounting of the damping system on the motor shaftto be implemented as a press fit. In this design, the pressing force oradhesion of the sliding disk on the motor shaft is greater than that ofthe sealing disk. Just one reason for this is the fact that the sealingdisk, in contrast to the sliding disk, is pressed onto the motor shaftvia the elastically deformable damping material, which also permits acertain movability of the sealing disk on the motor shaft. Thismovability has the advantage that, during assembly, which is to say whenthe two disks are slotted together to join them into the damping system,at least the sealing disk can execute an axial motion along the motorshaft toward the sliding disk.

Subsequent to a first 120° relative rotation between the two disks, theinterlocking connection is established between the detent webs of thesealing disk and the cams of the sliding disk, so that both disks andthus the entire damping system are firmly seated on the motor shaft androtate therewith relative to the stationary shaft bearing or sphericalbearing. In order to capture friction bearing oil thrown outward by thecentrifugal force and return it to the bearing, the sealing disk ispreferably designed in the manner of a dish with an oil splash collarfacing inward at the circumference of the disk.

The thermoplastic elastomer that is suitably chosen as the material forthe sliding disk, in particular a thermoplastic copolyester(HYRTEL®—thermoplastic polyester elastomer), has sliding frictionproperties that are especially suitable for the material pairing withthe spherical bearing, which is typically made of steel.

The advantages achieved with the invention are, in particular, in thefact that the noises or sounds usually produced by axial shaft excursionon the one hand, and by the armature/impeller system and/orcommutator/brush system on the other hand, are damped considerably, atleast, by the use of a suitable damping system, preferably in bothbearing locations of the motor shaft of an electric motor fan drive. Asa result, the sound level of the structure-borne sound of the overallsystem, in particular including speed-dependent local sound levels inthe range of the resonant frequencies of the housing or system parts, isreduced considerably over the speed range of the electric motor.

Due to the use of a clamping collar, known per se, which is insertedbetween the shaft bearing and the damping system, and which braces onthe circumferential side against the end plate, the shaft bearing—whichis usefully implemented as a spherical bearing—is pressed reliablytowards the end plate opposite the damping system.

Further, the scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 is a partial longitudinal section of an electric motor drive fora heating and air conditioning fan in a motor vehicle with abrush-system-side spherical bearing and an opposing-side sphericalbearing, with a damping system according to the invention;

FIG. 2 is a perspective view of the inventive damping system in apreinstallation state with, arranged on the motor shaft, an annularsealing disk and a spring washer, as well as an annular sealing disk onthe spherical bearing on the brush system side;

FIG. 3 is a longitudinal section of the damping system in contact withthe spherical bearing in the assembled state with system disks slottedtogether to form defined spring travel; and

FIG. 4 is a view of the rear of the damping system facing the commutatorof the electric motor drive.

DETAILED DESCRIPTION

Corresponding parts are labeled with the same reference characters inall the figures.

FIG. 1 shows an electric motor drive in the form of a commutator motor 1with a motor housing (pole housing) 2, on whose inner circumference areheld a number of curved field or permanent magnets 3 corresponding tothe number of poles of the motor 1. In a manner that is not illustratedin detail, a motor shaft 4 bears the armature (rotor) 5 of thecommutator motor 1, which is implemented as a rotor lamination stackwith rotor windings wound therein. In a manner that is not illustratedin detail, a commutator 6, likewise mounted on the motor shaft 6, hascommutator bars with bar connections that are connected to the rotorwindings of the armature 5. The bars of the commutator 6 are contactedby brushes in a manner known per se. This side of the motor isfrequently also called the brush side or brush system side, orabbreviated BS (BS side). The opposing side is labeled AS (AS side).

At these two sides BS and AS of the commutator motor 1, a brush-side endplate 7 is fastened to the motor housing 2 at the end of the motorclosest to the commutator.

At the opposite shaft end of the motor shaft furthest from thecommutator an end plate 8 is fastened on the AS-side to the motorhousing 2. The two end plates 7, 8 accommodate spherical bearings 9 or10 in which the motor shaft 4 is rotatably supported by means of an oilfilm. The two stationary spherical bearings 9, 10 are each pressed andclamped against the applicable end plate 7 or 8 by means of a clampingcollar 11, 12. The clamping collar 11, 12 is braced against theapplicable end plate 7 or 8 in this design.

The commutator-side shaft end of the motor shaft 4 projects on the BSside out of the end plate 7 with a sufficiently long shaft section 13 toaccommodate a fan rotor of a heating and air conditioning fan of a motorvehicle in the manner known according to FIG. 1 of DE 295 13 633 U1,which is incorporated herein by reference the hub of which fan rotor ispressed onto this shaft section of the motor shaft 4 there. Thecommutator motor 1, which during the rotation thereof drives the fanrotor, thus serves as the fan drive.

As can be seen comparatively clearly from FIGS. 2 and 3, a dampingsystem 14 preferably is provided on both the BS side bearing locationand the AS side bearing location. This system is placed on the motorshaft 4 at the bearing side of the spherical bearing 9 or 10 facing awayfrom the applicable end plate 7, 8. The damping system 14 takes up theaxial play extending in the longitudinal direction of the motor shaft 4.

The damping system 14 serves, firstly, to attenuate impact noises thatare caused by the axial excursion of the system composed of the armature5 and commutator 6, including motor shaft 4, of which the fan rotor isalso a part in the case of the fan drive. The damping system 14 thusreduces the sound level and also attenuates the noises that are known as“ooo” or whining noises generated by the commutator/brush system. Thecorresponding noise development is attributed to disturbances at eachrotation of the motor that are caused by the relative motion of thecommutator bars and the brushes traveling over them. In the relativelylarge plastic housing, these disturbances cause characteristic noises atresonant points specific to the housing parts.

As shown in FIGS. 2 and 3, the damping system 14 is composed primarilyof a sealing disk 15 and a sliding disk 16, along with a wave spring 17located between them. The sliding disk 16 faces the applicable sphericalbearing 9, 10.

As can be seen relatively clearly in FIG. 3, a defined spring travel “a”is formed between the sealing disk 15 and the sliding disk 16. Thistravel is approximately 0.2 mm. In the assembled state of the dampingsystem 14 that is shown, the wave spring 17, which like the sealing disk15 and sliding disk 16 sits on the motor shaft 4, is located betweenthese two disks 15 and 16. In this arrangement, a damping element 18,which is formed on the sealing disk 15 and made in an annular shape,coaxially surrounds the wave spring 17.

The damping element 18 preferably is a component of the sealing disk 15that is made as a single piece therewith. The damping element 18 is madeof a damping material that is relatively soft compared to the relativelyhard material of the rest of the sealing disk 15. A shaft seal 19, whichlikewise is made of the damping material and again is made as a singlepiece with the rest of the sealing disk 16, grips around the motor shaft4, and in so doing forms a cylindrical or sleeve-like seal transition tothe sealing disk 15 on the motor shaft 4.

This shaft seal 19 is approximately L-shaped in cross-section, as shownin FIG. 3. In this design, an axial branch 19 a of the L surrounds themotor shaft 4 in the transition region or opening region of the sealingdisk 16, while an adjoining radial branch 19 b of the L extends on therear 20 of the sealing disk 15, engaging behind the disk there. Theradial branch 19 b of the L acts as contact damping of the dampingsystem 13 with respect to the commutator 6.

This contact damping at the commutator 6 is supported by additionaldamping webs 21, which are visible in FIG. 4, which shows the rear 20 ofthe sealing disk 15. The damping webs 21 are likewise made of thecomparatively soft damping material. As a result of the sealing disk 15preferably being produced from a two-component plastic in the injectionmolding process, this material extends from the inner side of thesealing disk facing the sliding disk 16 to the opposite rear side 20 ofthe disk through local omissions of material.

The comparatively soft damping material forms the annular dampingelement 18 on the inner side as well as the shaft seal 19 and the threeouter-side damping webs 21 of the sealing disk 15. In order to protectthe commutator 6, this sealing disk is designed in a dish shape with anoil splash collar 22 for capturing friction bearing oil that is thrownoutward for operational reasons.

As FIG. 2 shows, three detent elements 23 that are offset from oneanother by 120° in degrees of arc are formed on the sealing disk 15;each of these detent elements includes a detent web 23 a with detent cam23 b molded on the end. When the sealing disk 15 and the sliding disk 16are slotted together, these detent cams 23 b, and hence the detentelements 23, engage behind the sliding disk 16. In this way, the sealingdisk 15 that is pressed onto the motor shaft 4 is axially movabletowards the sliding disk 16, which likewise is pressed onto the motorshaft 4 but is practically immovable, and the sealing disk is thus fixedin place thereon by the fact of being slotted together.

Formed on the sliding disk 16 are carrier cams 24, again offset by 120°.When the sealing disk 15 is slotted together with the sliding disk 16,these cams are each located in a random position between two of thethree detent elements 23 of the sealing disk 15. As a result of thefirst motor actuation of the drive 1, the carrier cams 24 will makeinterlocking contact with the closest detent elements in thepredetermined direction of rotation of the motor shaft 4 so that thedamping system 14 is then established as a rigid disk structure withenclosed wave spring 17.

Since the damping system 14 rotates synchronously with the motor shaft4, and hence also with the commutator 6, only contact or pressingeffects need to be taken into account on the commutator side, whereas arelative motion between the damping system 14 and the stationaryspherical bearing 9, 10 is present on the opposing bearing side foroperational reasons. Consequently, sliding or friction effects must betaken into account there, so that it is advantageous for the slidingdisk 16 to be made of a suitable sliding material or to be provided withsuitable antifriction properties. For this purpose, a thermoplasticelastomer, such as a thermoplastic copolyester marketed by the DuPontcompany under the name Hytrel, is especially suitable as a sliding diskmaterial.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

What is claimed is:
 1. An electric motor drive comprising: a commutatormotor whose motor shaft is rotatably supported on axially opposite sidesin shaft bearings that are each covered by an end plate; and a dampingsystem for sound damping of bearing-play-related impact noises andoperation-related whining noises is arranged on a bearing side facingaway from the end plate of the shaft bearing, wherein the damping systemhas a sealing disk, which is axially movable on the motor shaft, and asliding disk that faces the shaft bearings, wherein the damping systemhas a spring element or a wave spring in the manner of a spring washer,and wherein the damping system has a damping element on an inner side ofthe sealing disk facing the shaft bearing.
 2. The electric motor driveaccording to claim 1, wherein a spring travel between 0.1 mm and 0.5 mmor between 0.1 mm and 0.3 mm or less than 0.2 mm is established betweenthe sealing disk and the sliding disk.
 3. The electric motor driveaccording to claim 1, wherein the spring element is arranged between thesealing disk and the sliding disk.
 4. The electric motor drive accordingto claim 1, wherein the spring element is disposed between the motorshaft and the damping element of the sealing disk in the damping system.5. The electric motor drive according to claim 1, wherein the dampingsystem has a shaft seal between the sealing disk and the motor shaft. 6.The electric motor drive according to claim 5, further comprisingdamping webs disposed on the sealing disk, wherein the sealing disk andthe damping element along with the shaft seal and the damping webs areformed as a single piece from a two-component plastic with a relativelyhard sealing disk and a relatively soft damping material as the dampingelement, shaft seal, and damping webs.
 7. The electric motor driveaccording to claim 5, wherein the shaft seal is approximately L-shapedin cross-section and has an axial branch of the L extending along themotor shaft, and a radial branch of the L that engages behind thesealing disk on the disk rear facing away from the shaft bearing.
 8. Theelectric motor drive according to claim 1, wherein the sealing disk hasa number of damping points in the form of arcs.
 9. The electric motordrive according to claim 1, wherein the sealing disk and the slidingdisk are slotted together.
 10. The electric motor drive according toclaim 9, wherein, formed on the sealing disk are a plurality of detentelements with detent webs that are oriented toward the sliding disk anddetent cams provided thereon that engage behind the sliding disk. 11.The electric motor drive according to claim 10, wherein three detentelements are arranged such that they are evenly distributed with respectto one another.
 12. The electric motor drive according to claim 1,wherein the sealing disk is configured in the manner of a dish with anoil splash collar oriented towards the shaft bearing.
 13. The electricmotor drive according to claim 1, wherein the sliding disk has, on acircumferential side, a plurality of carrier elements or wherein thesliding disk has three evenly distributed molded-on carrier cams. 14.The electric motor drive according to claim 1, wherein the sliding diskis made of a thermoplastic elastomer, in particular of a thermoplasticcopolyester.
 15. The electric motor drive according to claim 1, furthercomprising a clamping collar inserted between the shaft bearing and thedamping system, and which braces on a circumferential side against thebearing side.
 16. The electric motor drive according to claim 1, whereinthe electric motor drive is a fan drive of a motor vehicle.